Turtle humor pervades the St. Thomas University research team studying turtle behavior. The image on the bumper sticker shows how a small radio transmitter is glued to a turtle's shell to allow "Team Turtle" to track it.
(Pioneer Press photos by Dave Orrick)
(Pioneer Press photos by Dave Orrick)

A band of four people wander the frozen expanse. They’re led by a diviner of sorts, a woman with a gizmo that looks vaguely like a flimsy stepladder.

Waiving the contraption this way and that, she zeros in on a spot.

Nearby, her companions kick up the snow crust, aided by a fellow with a broom, and regularly discover a bright scrap of paper, encased in the ice, labeled something such as “TURTLE #7” or “TURTLE #6.”

These are turtle researchers from the University of St. Thomas. They call themselves “Team Turtle.”

But that’s not what’s weird.

What’s weird is the turtles are on the run.

“Turtle on the move!” announces Anna Stanislav, a senior biology major from St. Paul, on a recent day when I joined Team Turtle in their odd field work of an odd animal behavior that no one can explain.

“What? Here?” asks an incredulous Tim Lewis, the chair of St. Thomas’ biology department and the leader of the research project. He wheels around, alternately scanning the featureless snow beneath him and the shore, searching for his bearings. “Which one?”

“Four!” Stanislav replies. Her divining rod – an antenna that tracks radio transmitters glued to the turtles’ shells – has picked up Turtle No. 4’s whereabouts, somewhere under the ice.

“Really?” Lewis says to himself. He begins kicking at the snow and is joined by the broom-wielding John Moriarty, a turtle guru and the natural resources manager for the Ramsey County Parks and Recreation Department. Grant Schmura, a St. Thomas junior from Stillwater, functions as both snow-kicker and recorder of data.

“Turtle 4,” Lewis mutters. “Hmmm.”

They find the corresponding scrap of paper for Turtle 4’s location a week earlier not far away – not far in warm-blooded human terms. They pace off 10 feet.

Ten feet of movement is odd for a reptile that is essentially hibernating. The body temperatures of the painted turtles they’re studying hover around 39 degrees, roughly the same as the water, and their heart rates hover around four beats per minute. (The heart rate of a resting person is generally between 60 and 100 beats per minute.)

Hold on, you say. How do turtles survive under the ice all winter? No, they don’t let themselves freeze, like some frogs. And no, they don’t seek out air pockets, like muskrats.

The shelled reptile actually can process limited oxygen through its skin, specifically around their mouth and anus. Yes, anus; in a sense, turtles can breathe through their butts.

Google “turtle hibernation” and you’ll have a tricky time finding the truth about how painted turtles spend the winter. Most explanations describe burrowing down in the bottom of a pond and waiting for spring. The Wikipedia entry, for example, makes no mention of the fact that turtles move when hibernating.

That painted turtles walk along the bottom of an ice-covered lake has been known for generations. Moriarty has an undated winter spearfishing decoy of one such Chrysemys picta, suggesting anglers knew they can be food for fish.

Relatively recently, Canadian researchers used radio telemetry to track movements, and Lewis’ team uses similar techniques to track 10 painted turtles on Lake Judy, a 15-acre shallow pond that supports an astonishing population of about 2,000 turtles, according to Lewis, whose team studies about 150 turtles on 40 lakes, all part of several projects.

In the spring, researchers trap the Lake Judy turtles and glue radio transmitters to their shells. They are tracked by using GPS equipment to mark their locations, which are plotted into detailed maps of the lake.

No one knows why turtles – or at least some of them – move in the winter.

“There are a lot of possible reasons, but none for which we have much evidence,” Lewis explained.

The turtles could be searching for a mate – although they won’t do much about it at these temperatures. They could be following oxygen supplies or temperatures – although only some turtles move, while others hunker down. They could just be the herpetological equivalent of sleepwalking.

There is no current in Lake Judy. The turtles’ metabolism is so low that their digestive system won’t function. And moving, however mellow, expends precious energy at a time when the reptiles don’t have much to spare. No. 10 is the long-distance record holder of the bunch. It hustled more than 150 yards in a week, nearly halfway across the lake.

— With a heart rate around 4 beats per minute, turtles basically hibernate.

— A turtle doesn’t need air when hibernating; it gets oxygen from water via gill-like membranes in the mouth and, yes, the anus.

— With such slow metabolism, turtles can’t digest food during the winter.

— Some hibernating turtles move surprising distances – more than 150 yards in a week – under the ice, and no one knows why.

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